The present invention relates to plasma torches of the kind comprising a single gas supply pipe leading into metal electrode carrier means and dividing means for dividing the gas flow into a first flow of plasmagenic gas and a second flow of cooling gas. Torches of this kind will hereinafter be referred to as "monogas plasma torches".
It will be understood that the utilisation of a single circuit for supplying the plasmagenic gas and for cooling the main elements of the torch: electrode, nozzle, insulator, etc. . . . , is attractive because of the resulting uncomplicated structure.
However, the need for controlling the ratio between the two flows in precise manner despite substantial temperature variations occurring during operation, raises serious design difficulties. This is probably the reason why, to the Applicants' knowledge, no monogas plasma torch of any kind has been produced industrially, although their principle had been disclosed many years ago (see U.S. Pat. No. 4,024,373 and its corresponding French patent No. 2,275,270).
It is an object of the invention to provide a monogas plasma torch intended to be capable of operating in a satisfactory manner under actual conditions of utilisation.